Processes for producing optically active substances by asymmetric hydrogenation of various substrates have hitherto been known. At the asymmetric hydrogenation reaction, it is reported that complexes of transition metals such as ruthenium, iridium, rhodium, palladium, and nickel containing various optically active phosphines as ligands exhibit excellent performance as catalysts, and some of the catalysts are industrially employed (Asymmetric Catalysts in Organic Synthesis, Ed., R Noyori, Wiley & Sons, New York (1994)). Among the ligands, phosphorane-type ligands are disclosed and transition metal complexes containing the ligands are reported to be excellent catalysts for asymmetric hydrogenation ((1) J. Organometal. Chem., 1987, 328, 71; (2) WO 91/17998 (BPE); (3) WO 93/01199 (DuPHOS); (4) J. Org. Chem., 1998, 63, 8031 (RoPHOS); (5) WO 00/11008; (6) WO 99/59721 (PennPhos); (7) WO 00/26220; and so forth).
However, all the phosphorane-type ligands shown in (1) to (6) contain two optically active phosphorane rings per one molecule, so that their preparation requires a large amount of expensive optically active 1,3- or 1,4-diols. Moreover, in the synthesis of the diphosphine shown in (7), it is necessary to introduce an optically active center onto a phosphorus atom, which is difficult to synthesize. Thus, there is an inconvenience that these ligands are not suitable for practical use.
Moreover, there are known processes for producing optically active amides by asymmetric hydrogenation of α,β-unsaturated amides, but processes excellent in optical purity or selectivity are few, and only the processes requiring the amount of catalyst relative to the substrate (so-called S/C) of about 500 to 1000 are known.
Since the optically active amides are important not only as compounds having certain uses as they are but also as synthetic intermediates for other useful compounds, it has been desired to develop a more advantageous process for the production.